Load Factor: Reading Airline Density
Load factor as RPM ÷ ASM vs IATA's RPK ÷ ASK; FY2025 IATA regional benchmarks; why a full plane is not a profitable one; capacity growth vs density.
Educational analysis for professional use. This guide is not investment advice or a recommendation to buy or sell any security, and it is not personalised.
Load Factor Measures Seats Filled, Not Margins
A full plane can still lose money. Load factor is the share of seats flown with a paying passenger aboard. It feeds unit revenue, but a plane can be full at fares below its cost per seat-mile.
Definition: Carrier Filing vs IATA
US carriers divide revenue passenger miles (RPM: paying passengers times miles flown) by available seat miles (ASM: seats times miles). IATA, the airline trade body, does the same in kilometres (RPK ÷ ASK).
| Source | Formula | Notes |
|---|---|---|
| US carrier filing | RPM ÷ ASM | Southwest footnote (c); standard SEC operating-statistics line |
| IATA passenger load factor | RPK ÷ ASK | Same ratio in kilometres; FY2025 press release |
IATA FY2025 Regional Benchmarks
Mature network carriers usually fly in the low to high 80s per cent, a convention drawn from these IATA figures and US network filings; no regulator sets it.
| Region | Passenger load factor | Source as-of |
|---|---|---|
| Global | 83.6% | IATA, FY2025 |
| North America | 82.9% | IATA, FY2025 |
| Europe | 84.8% | IATA, FY2025 |
FY2025 Carriers Ranked by Load Factor
Load factor tracks the business model first. Low-cost (LCC) and ultra-low-cost (ULCC) carriers fly point to point; network carriers connect passengers through hubs.
| Carrier | Load factor | ASM / ASK growth | Model type |
|---|---|---|---|
| Southwest | 77.4% (−3.0 pts YoY) | ASM +1.6% | US point-to-point LCC |
| United | 82.2% | ASM +6.1% | US global network |
| American | 83.6% | ASM +2.2% | US network |
| Delta | 84% | ASM +3% | US premium-skewed network |
| International Airlines Group (IAG) | 85.6% | ASK +2.4% | European network group |
| Ryanair | 94% (booked basis; year to 31 Mar 2025) | ASM +9.2% | European ULCC |
Ryanair’s booked load factor counts seats sold, so a no-show still fills a seat; the other five count passengers flown. Its figure comes from point-to-point flying and its own fare structure, so it is no target for a hub carrier.
Network vs ULCC: Density Is Not Interchangeable
Adding seats and filling them are separate decisions. United grew on a 330,284m ASM base, Ryanair on 166bn. The load factors each reached reflect network shape, flight frequency and fare structure more than management skill alone.
Southwest’s load factor fell while its capacity barely grew, a pattern that usually means softer demand or schedule changes. Read it against Southwest’s own RASM (15.59¢) and ~3.2¢ ex-fuel unit spread.
IAG flies a transatlantic-heavy network on 351,435m ASK. Pair its load factor with passenger revenue per ASK (PRASK, 8.24 €c/ASK) and ex-fuel cost per ASK (CASK ex-fuel, 6.01 €c/ASK) for the economics, then with EBITDAR leverage to see how big a demand dip the balance sheet can absorb.
Worked Mini-Example: Load Factor and Revenue Passenger Miles
Take an illustrative 200bn ASMs/yr at TRASM (total revenue per ASM) of 18.0¢. Revenue per seat-mile equals revenue per passenger mile times load factor. Hold TRASM fixed and a higher load factor forces revenue per passenger mile down:
| Load factor | RPM (bn) | Revenue per RPM if TRASM stays 18.0¢ |
|---|---|---|
| 77.4% (Southwest FY2025) | 154.8 | ~23.3¢ |
| 82.2% (United FY2025) | 164.4 | ~21.9¢ |
| 94% (Ryanair FY2025) | 188.0 | ~19.1¢ |
That is the ULCC trade: fill more seats at lower revenue per passenger. Density alone does not raise unit revenue.
Now hold the price instead. On the same 200bn ASMs, load factor rising from 82.2% to 84% lifts RPMs from 164.4bn to 168.0bn (+3.6bn). At a constant passenger yield of about 19.7¢ per RPM (United’s FY2025 passenger revenue per ASM, PRASM, of 16.18¢ divided by 82.2%), that is roughly +$0.7B of passenger revenue from the same seats. In practice the extra seats go at cheaper fares and yield falls, which is the discipline test.
Capacity Discipline Screen
ASM growth is the supply decision. Judge it by two filed outcomes: the load factor trend (were the new seats filled?) and the PRASM or RASM trend (at what price?). No growth rate suits everyone, and an arbitrary 90% load-factor target misses the point. The test is whether the carrier’s spread and balance sheet survive the growth path it chose.
EBITDAR builds from a thin unit margin on seat miles, the leases are capitalised into net debt, and the value moves on what a small load-factor drop costs.
The Excel model is the primer's airline build live across 11 sheets: EBITDAR from seat miles and unit margin, leases capitalised into adjusted net debt, a through-cycle EV/EBITDAR valuation for a network carrier and a low-cost carrier, a load-factor downturn, a lease-adjusted leverage screen and a sensitivity grid. Change the unit revenue, fuel or leases and the value moves.
Frequently Asked Questions
- How is airline load factor calculated?
- US carriers define load factor as revenue passenger miles (RPM) divided by available seat miles (ASM). IATA's passenger load factor uses revenue passenger kilometres divided by available seat kilometres (RPK ÷ ASK). The concept is identical; the distance unit differs.
- What is a normal load factor for a network airline?
- IATA reported FY2025 regional passenger load factors of 82.9% for North America and 84.8% for Europe. By convention, mature network carriers run from the low 80s to the high 80s per cent. For FY2025, US network carriers filed Delta 84%, United 82.2% and American 83.6%. Ryanair reports 94% on a booked basis (year to March 2025) from an ultra-low-cost model, so it is no guide for a network carrier.
- Does high load factor mean an airline is profitable?
- No. Load factor measures seat utilisation, not unit revenue minus unit cost. Southwest ran 77.4% load factor in FY2025 while Ryanair ran 94%, yet profitability depends on RASM/CASM spreads, fuel and balance-sheet leverage. United grew ASMs 6.1% with 82.2% load factor; Ryanair grew ASMs 9.2% with 94% load factor.
- What is capacity discipline in airlines?
- Capacity discipline means growing available seat miles only when demand supports it without collapsing load factor or passenger unit revenue. There is no universal "right" ASM growth rate: compare each carrier's ASM growth against its load factor trend and PRASM/RASM trajectory, not against a single industry target.